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Abstract:

One embodiment is a method that extends a tape path to compensate for
misalignment between tape oh a reel and a head by exiting the tape twice
from a tape pack of the reel before reading or writing data at the head.

Claims:

1) A tape drive, comprising:a head to read or write data to tape for
recording data; anda drive reel onto which the tape is wound, wherein the
tape exits a tape pack of the drive reel, passes around a guide clement,
re-enters the drive reel, and passes partially around the tape pack
before exiting for the head to extend a tape path between the head and
the drive reel.

2) The tape drive of claim 1, wherein the tape path is extended to
compensate for the tape pack being off-center between two flanges of the
drive reel.

3) The tape drive of claim 1, wherein the tape path is extended to
decrease an angle of misalignment of the tape extending between the drive
reel and the head.

4) The tape drive of claim 1 further comprising, two guides positioned on
opposite sides of the head, and the tape path extends from the tape pack,
to the guide element, back to the tape pack, back to the guide element,
and then to one of the two guides before passing across the head.

5) The tape drive of claim 1, wherein the guide element is flangeless.

6) A method, comprising:extending a tape path to compensate for
misalignment between tape on a reel and a head by exiting the tape twice
from a tape pack of the reel before reading or writing data at the head.

7) The method of claim 6 further comprising, exiting the tape from the
tape pack at two different nip points.

8) The method of claim 6 further comprising, exiting the tape pack at a
first nip point, extending the tape around a guide element, entering the
tape pack at a second nip point, extending the tape around the tape pack,
and exiting the tape pack at a third nip point.

9) The method of claim 6, wherein the tape path is increased by a distance
equal to at least a first distance from the tape pack to a guide element
plus a second distance from the guide element to the tape pack plus a
circumferential distance partially around the tape pack.

10) The method of claim 6 further comprising, reducing disturbances to an
edge of the tape from flanges on a guide by increasing a length of the
tape path.

11) A tape drive system, comprising:a computer;a tape cartridge including
tape for recording data; anda tape drive receiving the tape cartridge,
being in communication with the computer, and including a head and a
drive reel, wherein the tape exits twice from a tape pack of the drive
reel before passing to the head to compensate for misalignment while the
tape unwinds from the drive reel.

12) The tape drive system of claim 11 further comprising, a guide element
that receives the tape from the tape pack and positions the tape back
onto the tape pack before the tape unwinds to the head.

13) The tape drive system of claim 11, wherein the tape exits the tape
pack at two different nip points and enters the tape pack at a third nip
point.

14) The tape drive system of claim 11, wherein the tape path is lengthened
in the tape drive to align the tape with respect to the head.

15) The tape drive system of claim 11, wherein the head is positioned
between two guides and the tape exits the tape pack, wraps partially
around a third guide, re-enters the tape pack, travels around the tape
pack, and exits the tape pack a second lime toward one of the two guides.

Description:

FIELD OF THE INVENTION

[0001]The invention relates to a tape drive and more particularly a tape
drive having an extended tape path length between a nip point and a tape
guide.

BACKGROUND

[0002]Tape drives store a vast amount of digital information on rolls of
magnetic tape and arc often used to backup information stored in computer
systems. In a typical drive, magnetic tape is stored on a supply reel
contained in a removable cartridge. During read and write operations, the
tape is passed at a very high speed along a series of guides that define
a tape path to a take up reel in the drive. The tape passes in close
proximity to an assembly of read heads and write heads that must be
precisely positioned over the desired tracks so data can be accurately
read or written.

[0003]As magnetic tape is wound onto a tape reel at high speed, the tape
entrains air which allows the tape to float over the tape pack. As the
tape floats, it drifts to the sides of the reel until the tape finally
settles against the top or bottom flange of the reel. The reel flanges
are relatively far away from the edge of the free length of tape to
prevent the tape from contacting the reel as the tape is winding. If the
free length of tape contacts the reel flanges, the impact will cause the
tape to abruptly move laterally and disrupt registration between the
read/write head and the data track location. Because of the clearance
needed to avoid contact with the reel flanges while winding onto the
reel, the tape pack ends up being misaligned in height from the tape
guides. As the tape is then pulled from that reel, the misalignment of
the tape pack with the tape guides can create excessive stress on the
edges of the tape. This misalignment also creates disturbances from the
guide flanges to the tape and causes track misregistration.

BRIEF DESCRIPTION OF THE DRAWINGS

[0004]FIG. 1 is a tape drive system in accordance with an exemplary
embodiment of the present invention.

[0005]FIG. 2 is a tape drive in accordance with an exemplary embodiment of
the present invention.

[0006]FIG. 3A is diagram showing a shortened tape path length extending
between a tape guide and drive reel in a tape drive in accordance with an
exemplary embodiment of the present invention.

[0007]FIG. 3B is diagram showing a lengthened tape path length extending
between a tape guide and drive reel in a tape drive in accordance with an
exemplary embodiment of the present invention.

[0008]FIG. 4A is a flow diagram for winding tape onto a drive reel in
accordance with an exemplary embodiment of the present invention.

[0009]FIG. 4B is a flow diagram for unwinding tape from a drive reel in
accordance with an exemplary embodiment of the present invention.

[0010]FIG. 5 is an alternate embodiment of a tape drive in accordance with
an exemplary embodiment of the present invention.

DETAILED DESCRIPTION

[0011]Embodiments in accordance with the present invention are directed to
apparatus, systems, and methods that extend a tape path length in a tape
drive between a nip point and a tape guide. When magnetic tape is being
pulled from a tape pack of a drive reel, the tape passes from the tape
pack, to a guide, and back onto the tape pack. The tape passes partially
around the tape pack and then exits a second time from the drive reel.
After exiting the tape pack for the second time, the tape passes to
another guide, past the head, and to a cartridge reel located in the tape
drive.

[0012]One embodiment provides a tape drive with an additional guide
element (such as a flangeless guide or roller) that is added to the tape
path to pull the tape from the pack earlier to increase the distance
between the nip point and the first guide element. This reduces the angle
of misalignment of the tape as it enters the first flanged guide element.
The effective length of the tape path can be extended without increasing
the size of the drive.

[0013]Exemplary embodiments increase, the effective, free length of tape
between a nip point of the tape, pack of the drive reel and the guide.
This is accomplished by placing a flangeless guide element (such as a
guide or roller) at another location around the reel which the tape wraps
around before then wrapping back on the tape pack itself and then
eventually entering the flanged guide element. This additional guide
peels the tape off farther upstream of the tape path and effectively
increases the free length of tape between the nip point and the flanged
guide clement. At a high rate of travel, the tape that wraps back over
the tape pack has a layer of entrained air under it which causes the tape
to freely float. The entire length of tape between the new nip point and
the guide clement is effectively free or unconstrained. Therefore, the
angle of misalignment between the new nip point and the flanged guide is
reduced by the ratio of the increase in the effective free length of
tape.

[0014]When the tape pack is not properly or centrally aligned or
off-center between the flanges of the reel, exemplary embodiments
lengthen an effect free length of tape or distance of tape travel to
compensate for this improper alignment. As such, the tape unwinds from
the drive reel in proper alignment with the tape guides and/or read and
write heads.

[0015]Exemplary embodiments eliminate stress imparted on the tape from
contact with guide flanges and flanges on the drive reel since the tape
being unwound and wound onto the tape pack of the drive reel is aligned
between the flanges of the drive reel. Further, problems associated with
misregistration at the read/write head caused by disturbances between the
tape and flanges arc eliminated.

[0016]Exemplary embodiments enable tighter track density on the tape, and
therefore higher storage capacity by reducing the disturbances to the
edge of the tape from the tape guide flanges. Manufacturing precision
required for the guides and guide flanges are also reduced since an
increase in the tape path length compensates for misalignment between the
tape pack and rollers. Furthermore, exemplary embodiments reduce the
precision required for the tape reel flanges. Tape life can also be
extended since the contact forces between the tape edges and guide
flanges are minimized.

[0017]FIG. 1 illustrates a tape drive system 11 that includes one or more
tape drives 2 (shown as tape drive A to tape drive N) with removable tape
cartridges 4 networked to one or more computers 6 (shown as computer A to
computer N).through wired and/or wireless links or networks 8.

[0018]FIG. 2 illustrates a tape drive 10 such as might be used in the tape
drive system of FIG. 1. In tape drive 10 in FIG. 2, magnetic tape 12 is
wound on a cartridge reel or supply reel 14 inside removable cartridge
16. When cartridge 16 is inserted into drive 10, tape 12 passes around a
first roller or guide 18, over head 20, around a second roller or guide
22, and winds onto, a tape pack 23 of a drive or take-up reel 24. The
tape passes partially around the circumference of the tape pack 23 and
then exits the drive reel 24 to a third roller or guide (guide element)
25. After passes at least partially around this third, guide 25, the tape
is directed back to the drive reel 24 for winding on the tape pack 23.

[0019]The head 20 includes an array of elements that read and record
information on tape 12. Generally, the head converts an electrical signal
to a form required to record the signal to a medium (a write element), or
reads a signal from a medium and converts it to an electrical signal (a
read element), or both. Tape drives typically use magnetic head elements,
where an electrical signal drives a time-varying magnetic field that
magnetizes spots, or domains, on the surface of the magnetic tape.

[0020]Head 20 is mounted to an actuator 26 that moves head 20 across the
width of tape 12. An electronic controller 28 receives read and write
instructions and data from a computer 6 (FIG. 1) or other host device.
Controller 28, which may include more than one controller unit, includes
the programming, processor(s) and associated memory and electronic
circuitry necessary to control actuator 26, head 20 and the other
operative components of tape drive 10. As actuator 26 carries head
assembly 20 back and forth across the width of tape 12, controller 28
selectively activates the head elements to read or record data on tape 12
according to instructions received from the host device.

[0021]FIGS. 3A and 3B illustrate lengthening of the tape path in
accordance with exemplary embodiments. Magnetic tape 100 extends between
a tape roller or guide 102 and a take-up reel or drive reel 104. The nip
point 106A for the drive reel 104 is the tangential location where the
magnetic tape 100 exits the tape pack 110 on the drive reel. The nip
point represents a tangential-location at a circle and is located at the
outer diameter of the tape pack or location where the tape enters or
exits the tape pack. The guide 102 also has a nip point 106B where the
tape enters the guide.

[0022]An effective free length of tape 112 extends between the nip point
106A of the drive reel 110 and the nip point 106B of the guide 102. When
the magnetic tape 100 is not centered between the flanges 120 of the
drive reel 104, the magnetic tape 100 becomes misaligned with the guide
102. The angle of misalignment (O) 114 causes the tape to improperly
align with the guide 102. Specifically, if the free length of tape
contacts the reel flanges 120, the impact will cause the tape 100 to
abruptly move laterally and disrupt registration between the read/write
head 20 (see FIG. 2) and the data track location. Because of the
clearance needed to avoid contact with the reel flanges while winding
onto the reel, the tape pack ends up being misaligned in height from the
tape guide 102. As the tape is then pulled from the drive reel 104, the
misalignment of the tape pack 110 with the guide 102 creates excessive
stress on the edges or sides of the tape 100. This misalignment also
creates disturbances from the guide flanges 122 to the tape 100 and
causes track misregistration.

[0023]As shown in FIG. 3B, the angle of misalignment (O) 114' is
significantly reduced since the effective free length 112' of tape 100 is
increased. In other words, by extending or lengthening the tape path in
the tape drive, misalignment between the tape pack 110 of the drive reel
104 and the guide 102 is reduced. This reduction in misalignment reduces
stress on the edges or sides of the tape 100 and decreases disturbances
induced from contact of the tape with the guide flanges 122.

[0024]As shown in FIG. 2, exemplary embodiments utilize an additional
roller or guide 25 to increase a length of the tape path or effective
free length of the tape 12. This increase is equal to a partial or almost
full circumference around the tape pack 23 plus distance from the tape
pack 23 to roller 25, plus the distance from the roller 25 back to the
tape pack.

[0025]The tape path length from the guide 22 to the drive reel 24 is
traditionally equal to a distance 150 that the tape extends from a nip
point 152 at the roller 22 to a nip point 154 at the tape pack 23.
Exemplary embodiments, however, significantly increase this tape path
length. This increase is equal to the following: a distance 160 that the
tape extends from the nip point 154 around the tape pack 23 to a second
nip point 162 of the tape pack, plus another distance 170 that the tape
extends from the nip point 162 to a first nip point 172 of the guide 25,
plus a distance 180 that the tape extends from the nip point 172 around
the guide 25 to a second nip point 174, plus a distance 190 that the tape
extends from the nip point 174 to the nip point 156 (which is located
very close to the nip point 154).

[0026]Typically, the physical size of the tape drive is a predefined form
factor having a relatively small space. Exemplary embodiments provide
methods and apparatus for increasing the length of the tape path inside
the tape drive as the tape passes from the cartridge reel to and from the
drive reel. Tape is pulled off the drive reel, wrapped around a guide,
and then back onto the tape pack of the drive reel to increase the length
of the tape path.

[0027]FIG. 4A is a flow diagram for winding tape onto a drive feel in
accordance with an exemplary embodiment of the present invention.

[0028]According to block 410, the magnetic tape is moved from the supply
reel or cartridge reel, past a first roller, past the head, past a second
roller, and onto the take-up reel or drive reel.

[0029]According to block 420, the tape then partially wraps around an
outer circumference of the tape pack on the drive reel. The tape then
exits the tape pack of the drive reel to a guide element (such as a guide
or roller) that is located in the tape drive adjacent the drive reel.

[0030]According to block 430, the tape passes around the guide element and
back onto the tape pack of the drive reel. Here, the tape is wound around
the tape pack of the drive reel.

[0031]FIG. 4B is a flow diagram for unwinding tape from a drive reel in
accordance with an exemplary embodiment of the present invention.

[0032]According to block 440, as the tape begins, to unwind from the tape
pack of the drive reel, the tape exits the tape pack to the guide
element.

[0033]According to block 450, the tape passes around the guide element and
back to the tape pack of the drive reel.

[0034]According to block 460, the tape passes partially around the outer
circumference of the tape pack of the drive reel. The tape then exits the
tape pack to a first guide or roller.

[0035]According to block 470, the tape passes past the first guide or
roller, past the head, past a second guide or roller and to the supply
reel or cartridge reel where the tape is wound.

[0036]Exemplar embodiments are not limited to any particular location of
the guide element 25. By way of example, FIG. 5 shows an alternate
embodiment of a tape drive 200 wherein like numerals refer to like
elements with respect to FIG. 2. As shown in FIG. 5, the guide clement 25
is moved to a corner of the tape drive 200.

[0037]Exemplary embodiments are not limited to any particular type, style,
shape, quantity, etc. of rollers and guides. By way of example, such
rollers and guides in the tape drive include both static guides (i.e.,
fixed or stationary guides that do riot rotate as tape passes around)
rollers (i.e., fixed or stationary guides that rotate as tape passes
around), and may include one or more guides between the head and either
reel.

[0038]Exemplary embodiments of the invention arc not limited to any
particular type of tape drive or magnetic tape. Further, although
embodiments are discussed with respect to the take-up or drive reel,
exemplary embodiments can also be utilized with a source or cartridge
reel. Also, other forms of tape are applicable, such as optical tape.

[0039]Definitions:

[0040]As used herein and in the claims, the following words have the
following definitions:

[0041]The term "effective length of tape" means length of tape path that
extends from a take-up or drive feel in a tape drive to a guide or roller
before the head.

[0042]A "head element" or "head" means a transducer that converts an
electrical signal to a form required to record the signal to a medium (a
write element), or reads a signal from a medium and converts it to an
electrical signal (a read element), or both.

[0043]The term "nip point" means a location or point where a free length
of tape is tangent to an outer diameter of a tape pack of a tape reel.

[0045]In one exemplary embodiment, one or more blocks in the flow diagrams
are automated. In other words, apparatus systems, and methods occur
automatically. As used herein, the terms "automated" or "automatically"
(arid like variations thereof) mean controlled operation of an apparatus,
system, and/or process using computers and/or mechanical/electrical
devices without the necessity of human intervention, observation, effort
and/or decision.

[0046]The flow diagrams in accordance with exemplary embodiments of the
present invention are provided as examples and should not be construed to
limit other embodiments within the scope of the invention. For instance,
the blocks should not be construed as steps that must proceed in a
particular order. Additional blocks/steps may be added, some blocks/steps
removed, or the order of the blocks/steps altered and still be within the
scope of the invention. Further, blocks within different figures can be
added to or exchanged with other blocks in other figures. Further yet,
specific numerical data values (such as specific quantities, numbers,
categories, etc.) or other specific information should be interpreted as
illustrative for discussing exemplary embodiments. Such specific
information is not provided to limit the invention.

[0047]In the various embodiments in accordance with the present invention,
embodiments are implemented as a method, system, and/or apparatus. As one
example, exemplary embodiments are implemented as one or more computer
software programs to implement the methods described herein. The software
is implemented as one or more modules (also referred to as code
subroutines, or "objects" in object-oriented programming). The location
of the software will differ for the various alternative embodiments. The
software programming code, for example, is accessed by a processor or
processors of the computer or server from long-term storage media of some
type, such as a CD-ROM drive, flash memory, or hard drive. The software
programming code is embodied or stored on any of a variety of known media
for use with a data processing system or in any memory device such as
semiconductor, magnetic and optical devices, including a disk, hard
drive, CD-ROM, ROM, flash memory, etc. The code is distributed on such
media, or is distributed to users from the memory or storage of one
computer system over a network of some type to other computer systems for
use by users of such other systems. Alternatively, the programming code
is embodied in the memory and accessed by the processor using the bus.
The techniques and methods for embodying software programming code in
memory, on physical media, and/or distributing software code via networks
are well known and will not be further discussed herein.

[0048]The above discussion is meant to be illustrative of the principles
and various embodiments of the present invention. Numerous variations and
modifications will become apparent to those skilled in the art once the
above disclosure is fully appreciated. It is intended that the following
claims be interpreted to embrace all such variations and modifications.